1. Technical Field
The present invention relates to a position information generation device, a timing signal generation device, an electronic apparatus, and a moving object.
2. Related Art
A Global Positioning System (GPS) using satellites is a widely used type of the Global Navigation Satellite Systems (GNSSs). Atomic clocks with considerably high accuracy are mounted on the GPS satellites used in the GPS, and thus the GPS satellites transmit satellite signals by which accurate time information or orbit information regarding the GPS satellites is transmitted to the ground. The satellite signals transmitted from the GPS satellites are received by GPS receivers. Then, the GPS receivers perform a process of calculating time information or the current positions of the GPS receivers, a process of generating an accurate timing signal (1 Pulse Per Second (PPS)) synchronized with a coordinated universal time (UTC), or the like based on the time information or the orbit information superimposed on the satellite signals.
Such GPS receivers are generally provided with a normal positioning (position estimating) mode in which a position and a time are supplied based on a positioning calculation and a fixed position mode in which a time is supplied through fixed position positioning at a known position.
In the normal positioning mode, satellite signals from a number of GPS satellites equal to or greater than a predetermined number (a minimum of three GPS satellites in the case of 2-dimensial positioning and four GPS satellites in the case of 3-dimensional positioning) are necessary. As the number of GPS satellites capable of receiving satellite signals becomes larger, the accuracy of the positioning calculation is improved.
In the fixed position mode, on the other hand, when the position information regarding the GPS receiver is set and when a satellite signal can be received from at least one GPS satellite, the 1 PPS can be generated.
Since the accuracy of the 1 PPS in the fixed position mode depends on the accuracy of the set position information, it is important to set accurate position information in the GPS receiver. As methods of acquiring the accurate position information set in the GPS receiver, for example, a method of reading position information from a map or a method of measuring position information can be considered. However, in the former case, it is difficult to acquire the position information depending on a reception location. In the latter case, there is a problem of cost such as expense or time.
In order to resolve such problems, JP-A-9-178870 suggests a method of performing positioning calculation with an installed GPS receiver, averaging position information regarding positioning results for a predetermined time, and determining the position of a reception point. According to this method, the position information can be acquired at any reception location and cost can also be reduced.
However, when a certain error such as multi-paths occurs, the position information regarding the result of the position calculation includes a large error. In the method of averaging the positioning calculation results in JP-A-9-178870, there is a probability that an error of the position of a reception point obtained as the result of the averaging may increase. For this reason, in the method of JP-A-9-178870, there is a problem that the accuracy of 1 PPS (timing signal) may deteriorate depending on a reception environment at the time of performing the positioning calculation. Such a problem is also common to GPS receivers and reception devices of the other Global Navigation Satellite Systems (GNSSs).